Molecularly targeted therapy has emerged as a promising approach to overcome the lack of specificity of conventional chemotherapeutic agents in the treatment of cancer. Synthetic peptide drugs in cancer therapy show high specificity, stability and ease of synthesis compared to conventional proteins. However, the delivery of these anti-cancer peptides to the target site poses huge problems due to factors like enzymatic degradation, immunogenicity and a short life span in the blood. Targeted delivery of anticancer drugs would be more effective if the delivery system was able to reach the desired tumor tissues through the penetration of barriers in the body with minimal loss of their volume or activity in the blood circulation and selectively kill tumor cells. This would improve patient survival and quality of life by increasing the intracellular concentration of drugs and reducing dose-limiting toxicities simultaneously. One of the strategies for delivery of peptide drugs involves conjugating peptides with cell penetrating peptides (CPP) for direct delivery of the drug into cytosol. However, conjugation with CPP increases the cost and decreases the efficacy and stability of peptide drugs, and can in some instances increase toxicity. Some peptidic therapeutic agents like NuBCP-9 and Bax-BH3 show selective binding to cancerous cells and initiate apoptosis. Unfortunately, free drug formulations of peptidic therapeutic agents require the use of large amounts and frequent administration of the peptide, thereby increasing the cost and inconvenience of therapy.
There is a pressing need for a delivery system that can effectively deliver therapeutic agents, including therapeutic peptides, into the cytosol of cancerous cells.